Technical Field
The present invention relates to an industrial robot provided with a horizontal multistage telescopic device.
Related Art
Industrial robots are equipped, as required, with a multistage telescopic device that needs only a small installation space relative to an aimed length of stroke (e.g., see JP-A-H09-028589 and JP-A-H11-245189). As such a multistage telescopic device, a horizontal multistage telescopic device has a basic configuration as roughly illustrated in FIG. 8. A part (a) of FIG. 8 illustrates a horizontal multistage telescopic device 100 that is in a state where a slider 102 and an output arm 104, which will be described later, are at their home positions (movement limitation positions relative to a direction indicated by an arrow X2). A part (b) of FIG. 8B illustrates the horizontal multistage telescopic device 100 that is in a state where the output arm 104 has been expanded to an aimed position of stroke.
As shown in the parts (a) and (b) of FIG. 8, the horizontal multistage telescopic device 100 has a base 101 which is arranged such that the slider 102 is movable in a direction of an arrow X1 (horizontally rightward in the parts (a) and (b) of FIG. 8) and in an opposite direction of the arrow X2. The slider 102 includes a movable block 103 which is made movable in the directions of the arrows X1 and X2 as well.
The output arm 104 has a left end portion which is mounted to the movable block 103. In other words, the output arm 104 is projected from the movable block 103 in the direction of the arrow X1. Although not shown in FIG. 8, the output arm 104 has a tip to which an end effector, such as a hand or a drill, is attached.
Further, the slider 102 includes a movement mechanism 105. The movement mechanism 105 is configured by pulleys 105a and 105b, as well as a belt 105c. The pulleys 105a and 105b are rotatably provided at both horizontal ends of the slider 102. The belt 105c is provided across the pulleys 105a and 105b and has two sides facing with each other. Of the two sides facing with each other in the belt 105c, one side has a portion 105h connected to the base 101, while the other side has a portion 105i, as a portion extremely opposite to the portion 105h, connected to the movable block 103.
The horizontal multistage telescopic device 100 includes a drive mechanism 110 which includes a motor 111, a rotation transmission mechanism 112 and a ball screw device 113. The motor 111 is mounted to the base 101 via a mounting end plate 101a. The ball screw device 113 includes a ball screw 113a and a nut case 113b. The nut case 113b has an interior in which a nut that threadably engages with the screw 113a is rotatably arranged. The ball screw 113a has an end which is fixed to the slider 102 via a mounting end plate 102a, while the nut case 113b is fixed to the base 101 via the mounting end plate 101a. 
The rotation transmission mechanism 112 plays a role of transmitting rotation of the motor 111 to the nut, and includes a pulley 112a mounted to the rotary shaft of the motor 111, a pulley 112b mounted to the nut and a belt 112c provided across these pulleys.
When the motor 111 of the drive mechanism 110 is rotated in a given direction, the nut is rotated in a given direction via the rotation transmission mechanism 112. Since the nut case 113b having the nut does not move, the ball screw 113a is pushed toward the direction of the arrow X1 by the rotation of the nut, permitting the slider 102 to move in the direction of the arrow X1. Thus, as mentioned above, the output arm 104 is permitted to move by a distance corresponding to an aimed stroke St (see the part (b) of FIG. 8).
Parts (a) and (b) of FIG. 9 illustrate an exemplification, or an actual configuration, of the horizontal multistage telescopic device illustrated in FIG. 8. The functional components identical with or similar to those shown in FIG. 8 are given the same reference numerals.
For example, as shown in a part (a) of FIG. 10, the horizontal multistate telescopic device 100 is assembled to a carrier device 200 and an elevator device 300 to configure an industrial robot. In this case, the base 101 is mounted to an elevator member 301 of the elevator device 300 which is incorporated into the carrier device 200. The carrier device 200 moves (carries) the elevator device 300 in a direction indicated by an arrow A1 (forward) and in an opposite direction indicated by an arrow A2. The elevator device 300 moves (lifts up and down) the horizontal multistage telescopic device 100 in a direction indicated by an arrow B1 (upward) and in an opposite direction indicated by an arrow B2. An end effector E, such as a hand or a drill, is mounted to a tip of the output arm 104 of the horizontal multistage telescopic device 100.
In a state shown in the part (a) of FIG. 10, the output arm 104 of the horizontal multistage telescopic device 100 is at a home position. From this state, the output arm 104 is moved in the direction of the arrow X1 so that the end effector E of the output arm 104 can reach a target coordinate M (see a part (c) of FIG. 10) residing in the direction of the arrow X1. A part (b) of FIG. 10 shows a state where the output arm 104 is in the midst of being moved. After that, the horizontal multistage telescopic device 100 is lifted down to a target position in the vertical direction by the elevator device 300. Then, the end effector carries out its work, such as gripping a work or releasing the grip, or drilling a work.
The horizontal multistage telescopic device 100 installed in industrial robots is used for assembling precision devices or performing precision machining. Therefore, the horizontal multistage telescopic device 100 is required to provide highly accurate performance, or have high movement speed as a robot from the viewpoint of productivity.
However, in the horizontal multistate telescopic device 100 based on conventional art, when the output arm 104 has been moved to the target coordinate M, the tip of the output arm 104 can finely vibrates up and down (i.e., residual vibration). For this reason, positioning at the target coordinate M is difficult, which leads to impairing assembling or working accuracy. A measure against this problem may be to wait until the convergence of the residual vibration. However, such a measure leads to lowering of the movement speed of the robot and lowering of productivity.